Tamper evident caps for containers, such as blow-molded or injection molded containers are well known, see e.g., U.S. Pat. Nos. 4,561,553, 4,625,875, 4,497,765, and 4,534,480. A number of caps are of the snap-on screw-off variety such as U.S. Pat. Nos. 5,190,178, 5,213,224 and 5,307,946. Generally, the prior art caps include a spiral thread or threads which match a spiral thread on the neck of the bottle. In the '946 patent, the cap and bottle neck include a seven lead-in end annular spiral threads or fastening means. The stated advantage of the multiple lead-in threads of the '946 patent is the increased ease of "snap-on" placement of the cap onto the threaded neck using standard bottle capping equipment and without an additional tightening step such as a final twist.
As is apparent from the prior art patents, a great deal of effort has gone into design of cap and bottle neck configurations to provide easy on and off use of the cap by the bottler and ultimately by the end user of the bottled product. However, notwithstanding this effort, the bottling industry continues to search for a cap and neck finish which achieves these objectives, but which also provides a secure seal. In addition, the ultimate consumer of the bottled product desires a cap which is easy to use both in removal from the bottle but also as reapplication on to the bottle.
Accordingly, it is an object of the present invention to provide a bottle neck finish and tamper evident cap for use therewith which is easy for the bottler to place on the filled container without additional tightening operations, but is substantially leak-proof. Also it is an objective of the invention to provide a container neck finish and cap which permits the end user to readily remove the cap after the tamper-evident means is removed by either lifting or twisting the cap from the neck. The present invention also permits the ultimate user to snap-on the cap or screw-on the cap to provide a leak-tight seal. A further object of the invention is to provide a neck finish for blow molded containers and a high or low density plastic bottle cap which can be snap or screw fit on to the container. It is also an object of the invention to provide a cap which snap fits onto a neck finish which does not have snap locks.